The present invention generally relates to an apparatus and methodology for combining multiple electrical power storage and/or generation systems, henceforth also referred to as power units, so that a desired combination of cost and effectiveness can be achieved by efficiently switching power into, out of, and/or around the power units to supply power to a load.
There is a growing need for the electrification of the transportation industry, and to supplement the electric power generation and distribution system (the electric utility grid) by storing energy at times when the grid has excess capacity, and releasing energy into the grid at times when generation and/or grid usage approaches maximum capacity. In addition, the cost and efficiency of storing and generating electrical power to run portable appliances has become increasingly important. The system disclosed herein can provide an efficient and convenient methodology to combine multiple electrical power storage and/or generation systems (power units) so that a desired combination of cost and effectiveness can be achieved by efficiently switching power into, out of, and/or around the power units.
In the transportation vehicle industry (including watercraft) where electrical power is used, there are internal combustion engine hybrids, fuel cell hybrids, and battery electric vehicles. In the portable appliance industry, manufacturers of portable media appliances such as mobile computers, telecommunication devices, and other entertainment devices are constantly searching for an optimum mix of cost and performance in their electrical power systems. As new and different power storage and generation methodologies evolve, there may be additional modes of power for these transportation vehicles and portable appliances. The system disclosed herein can assist in finding a desired mix of existing and future energy generation and/or storage units for these industries as well as other industries facing energy generation and/or storage issues.
The utility industry is constantly searching for more efficient ways to store energy in times of excess capacity and to release energy to supplement generation at times of peak demand. In the process, various additional peak time generation units are brought online and energy storage units are discharged. The system disclosed herein can assist in combining a desired mix of energy generation and/or storage units for the utility industry and to provide backup power as well as supplemental power
Different power storage and power generating units have different cost and performance characteristics. These characteristics include, but are not limited to:                Financial cost: the cost per unit of energy stored or generated;        Energy density: the weight and volume of the module versus the amount of energy stored/delivered;        Energy efficiency: the rate of storage and discharge of energy, and/or the efficiency (minimal energy loss) in storage and discharge of energy;        Cycle Life: the useful life of the module (charge, discharge and/or energy generation life), and the stability of chemistry and/or structure;        Safety: the thermal stability, chemical inertness, energy and/or chemical containment in the event of breach of containment; and        Environmental operating range: the temperature, humidity, vibration, corrosive resistance, etc.The system disclosed herein can be used in developing a combination of power generation and/or storage units that balances these characteristics while meeting desired objectives.        
The energy transfer circuit can connect a load to multiple energy sources. The energy transfer circuit includes a load connection for connecting the load to the energy transfer circuit; a first source connection for connecting a first energy source having a first voltage to the energy transfer circuit; a second source connection for connecting a second energy source having a second voltage to the energy transfer circuit; and a control unit for receiving communications regarding the load, the first energy source and the second energy source. The first voltage of the first energy source can be the same as or different from the second voltage of the second energy source. The energy transfer circuit transfers energy from at least one of the first energy source and the second energy source to the load when the control unit receives a power demand from the load, transfers energy from the load to at least one of the first energy source and the second energy source when the control unit receives a charging current from the load; and transfers energy from either of the first and second energy sources to the other of the first and second energy sources when the control unit determines an energy transfer is necessary. The control unit can also respond to a highpower demand from the load, by controlling the energy transfer circuit to simultaneously transfer power from both the first and second energy sources to the load.
The energy transfer circuit can connect a load to a primary energy source having a first voltage and a secondary energy source having a second voltage. The energy transfer circuit can includes a first capacitor connected in parallel with the primary energy source and connected in parallel with the load; a second capacitor connected in parallel with the secondary energy source; an inductor; a first switch between the inductor and the first capacitor; a second switch between the inductor and the second capacitor; and a control unit receiving communications regarding the load, the primary source and the secondary source. The control unit controls the opening and closing of the first switch and the second switch in response to the communications. The energy transfer circuit enables the primary energy source and the secondary energy source to have different voltages. The energy transfer circuit also enables the load to draw power from either or both of the primary and secondary sources. The energy transfer circuit also enables the load to charge either or both of the primary and secondary sources. The energy transfer circuit also enables either of the primary and secondary sources to charge the other of the primary and secondary sources. Either of the first and second switches can be a unidirectionally protected switch.
The energy transfer circuit can also include a first diode in parallel with the first switch, where the first diode is biased to conduct current from the inductor towards the first capacitor. The energy transfer circuit can also have a second diode in parallel with the second switch, where the second diode is biased to conduct current from the inductor towards the second capacitor. The energy transfer circuit can also include a third switch between the primary energy source and the load.
The energy transfer circuit can also include a first sensor coupled to the primary energy source that transmits communications to the control unit regarding the status of the primary energy source. The energy transfer circuit can also include a second sensor coupled to the secondary energy source that transmits communications to the control unit regarding status of the secondary energy source. The control unit can also determine the state of charge of the primary and secondary energy sources, and can control the transfer of energy between the primary and secondary energy sources using the first and second switches.
The control unit can receive power demands from the load, and control the first and second switches to transfer energy from at least one of the primary and secondary energy sources to the load. The control unit can receive charging currents from the load, and control the first and second switches to transfer energy from the load to at least one of the primary and secondary energy sources.
A method for transferring energy to and from a load is also disclosed. The method makes use of an energy transfer circuit that includes a first capacitor, a second capacitor, an inductor, a first switch between the inductor and the first capacitor, a second switch between the inductor and the second capacitor, and a control unit. The method includes connecting the load in parallel with the first capacitor of the energy transfer circuit; connecting a primary energy source having a first voltage in parallel with the first capacitor of the energy transfer circuit; and connecting a secondary energy source having a second voltage in parallel with the second capacitor of the energy transfer circuit. The method further includes communicating status information from the primary energy source to the control unit; communicating status information from the secondary energy source to the control unit; and communicating energy requests from the load to the control unit. The method also includes controlling the opening and closing of the first switch and the second switch using the control unit; responding to charging currents from the load; responding to power demands from the load; responding to energy requests for the primary energy source and the secondary energy source; and keeping the first switch and the second switch open unless responding to the charging currents, power demands or energy requests from the load, the primary energy source or the secondary energy source.
Responding to charging currents from the load can include determining whether either of the primary or secondary energy sources has a charge priority; charging the primary energy source when the primary energy source has the highest charge priority; charging the secondary energy source when the secondary energy source has the highest charge priority; running a trickle charge routine when neither of the primary energy source or the secondary energy source has the charge priority; and discontinuing the response to the charging current from the load when the charging current ceases or after a limited time.
Charging the primary energy source can include keeping the first and second switches open to charge the primary energy source with power from the load.
The energy transfer circuit can also include a second diode connected in parallel with the second switch, where the second diode is biased to conduct current from the inductor towards the second capacitor. The charging of the secondary energy source can include closing the first switch and keeping the second switch open to charge the inductor with power from the load; then opening the first switch and discharging the inductor through the second diode to charge the secondary energy source; then repeating these steps at a desired frequency to charge the secondary energy source. Charging of the secondary energy source can also include closing the second switch after opening the first switch and discharging the inductor through the second switch to charge the secondary energy source; and then opening the second switch and continuing to discharge the inductor through the second diode to charge the secondary energy source.
Responding to power demands from the load can include determining whether the power demand is a multiple source power demand or a single source power demand; executing a highpower routine when the power demand is the multiple source power demand; and executing a single unit power routine when the power demand is the single source power demand.
Executing a highpower routine can include determining whether the primary energy source is in a primary highload operating range; determining whether the secondary energy source is in a secondary highload operating range; transferring power from both the primary and secondary energy sources to the load when the primary energy source is in the primary highload operating range and the secondary energy source is in the secondary highload operating range; monitoring the state of charge of the primary and secondary energy sources; discontinuing the highpower routine when the primary energy source goes outside the primary highload operating range; discontinuing the highpower routine when the secondary energy source goes outside the secondary highload operating range; discontinuing the highpower routine when the power demand ceases; and discontinuing the highpower routine after a limited time.
The energy transfer circuit can also include a first diode in parallel with the first switch and a second diode in parallel with the second switch, where the first diode is biased to conduct current from the inductor towards the first capacitor, and the second diode is biased to conduct current from the inductor towards the second capacitor. In this case, transferring power from both the primary and secondary energy sources to the load can include providing power to the load from the primary energy source regardless of the positions of the first and second switches; closing the second switch and keeping the first switch open to charge the inductor with power from the secondary energy source; opening the second switch and discharging the inductor through the first diode to charge the load; closing the first switch after opening the second switch and discharging the inductor through the first switch to charge the load; opening the first switch and continuing to discharge the inductor through the first diode to charge the load; and repeating these four steps at a desired frequency to charge the load.
Executing a single unit power routine can include determining an operating condition of the primary energy source; determining an operating condition of the secondary energy source; transferring power from the primary energy source to the load when the primary energy source is in as good or better operating condition than the secondary energy source; transferring power from the secondary energy source to the load when the secondary energy source is in better operating condition than the primary energy source; discontinuing the single unit power routine when the power demand ceases or after a limited time.
The energy transfer circuit can also include a first diode in parallel with the first switch and a second diode in parallel with the second switch, where the first diode is biased to conduct current from the inductor towards the first capacitor, and the second diode is biased to conduct current from the inductor towards the second capacitor. In this case, transferring power from the secondary energy source to the load can include closing the second switch and keeping the first switch open to charge the inductor with power from the secondary energy source; opening the second switch and discharging the inductor through the first diode to power the load; closing the first switch after opening the second switch and discharging the inductor through the first switch to power the load; opening the first switch and continuing to discharge the inductor through the first diode to power the load; and repeating these four steps at a desired frequency to charge the load.
It is expected that as new and better battery, energy storage, and energy generation technologies evolve, various combinations of existing and future technologies can be leveraged using the present invention.